U.S. Pat. No. 3,722,463 issued to Kudo, et al., a further development of U.S. Pat. No. 3,122,114, issued to T.H. Kringel, et al., clearly demonstrates the economies associated with hot-galvanizing tubing in a continuous manner. In this regard, U.S. Pat. No. 3,722,463 relates to a process and means exclusively matched as to design and, hence, exclusively suited for hot-galvanizing of smooth tubes. One individual smooth tubes are joined to form a continuous tube, pre-treatment of the joined-together smooth tubes comprises a fluxing agent treatment (zinc-ammonium-chloride) and subsequent drying at about 200.degree. C. This mode of galvanizing entails, through sublimation of the fluxing agent, considerable exhaust air volumes laden with large quantities of harmful substances. Requirements having to do with environmental control can be met here only by way of an exhaust air trapping means and a purifying system connected therebehind, with this substantially reducing the economy of the system as a whole. Moreover, this known process and means for hot-galvanizing tubes is suited exclusively to smooth tubes.
The invention underlying the subject application, by contrast, relates to a process and means for galvanizing finned tubes, without the classic fluxing agent treatment and its negative environmental consequences, and with careful consideration of the specific requirements for hot-galvanizing and manipulating finned tubes.
The finned tube consists substantially of an oval base tube (or of other cross-section), onto which there is continuously, diagonally wound a sheet of metal fin according to the winding method employed. The finned tube is in no way bound to the base tube and often is of a substantially different material or thickness, and hence the finned tube willl often exhibit divergent coefficients of thermal expansion. The pitch of a typical finned tube amounts to approximately 3 mm; so that the surface area of a finned tube may be 40 times that of a smooth tube of comparable size and shape.
Prior art in conjunction with hot-galvanizing of finned tubes is the immersion into a zinc melt with preceding degreasing, rinsing, pickling, rinsing, and fluxing. These preliminary treatments are individual, separate operations, with the finned tubes being respectively dipped into individual baths containing the corresponding degreasing, rinsing, pickling, or like medium, e.g. by means of a crane. Cooling takes place in a water bath so that an immediate further treatment of the finned tube after galvanizing, is in qualified manner not possible.